Keeping good records is part of good battery maintenance, and can help you identify trends and spot problems if they occur.

Overcharging can result in excess gassing and loss of water. Exposed plates will oxidize and the battery will be permanently damaged.

Undercharging can result in electrolyte stratification and/or sulfation (shown) and a damaged battery.

Intermediate

Good design and installation practices are essential to a well-functioning inverter–battery system, but that is only a start. This article will review the ongoing battery maintenance that is crucial to a system’s longevity.

Adding Water

For flooded lead-acid (FLA) batteries, it is critical to check the electrolyte level on a regular basis. As batteries charge, some water in the electrolyte is converted to hydrogen and oxygen gas, and released through the vent caps. The electrolyte needs to be replenished to the proper level by adding distilled water.

In cool climates such as Washington State, a system with a moderate C/10 charge rate should be checked every one to two months. In hot climates like Haiti, the electrolyte level needs to be checked at least twice a month.

Recording the date and the amount of water added to the battery allows you to identify usage trends and spot potential problems. Batteries in hotter climates will use more water than ones in cooler climates, as will systems with heavy discharging and higher charging rates. When a battery starts requiring more water, it is typically a sign that it is failing—or that something has dramatically changed in the charging or load profile. Keeping track of the changes in water consumption will help determine when it’s time to replace the battery or investigate other problems.

The correct electrolyte level is usually about 1/4 inch below the vent tube. Adding water to a battery cell should be done only after charging the battery to 100% or after an equalization charge has been completed. However, if the plates inside the battery are close to being exposed (which can cause permanent damage to the battery), add enough water to keep them covered before recharging. However, be careful not to overfill during recharging or equalization. Otherwise, the electrolyte can overflow, making a hazardous mess. Losing electrolyte and replacing it with distilled water results in dilution, effectively reducing the battery’s capacity and, therefore, its performance. Automatic watering systems and recombination caps can reduce the time required for refilling batteries. However, most of them require removal before doing an equalization charge on the batteries.

Cleaning Battery Terminals

Corrosion can occur on and between the cable lugs and the battery terminals, creating higher resistance that impedes the flow of current when charging or discharging. Corrosion can also occur between battery terminals and the metal casing of the battery rack, potentially resulting in ground faults and creating a shock hazard.

If even only one terminal has corrosion, the high resistance on that series-connected string of batteries will result in less charging and discharging. Specifically, the other battery strings will compensate for the loss of total capacity, and be charged and discharged at higher rates. This will create imbalances within the battery bank, reduce system performance, and decrease the life and performance of the entire battery bank.

During the monthly inspection, check all battery connections for corrosion. If there’s a metal rack or enclosure, also check for corrosion between the terminals and the metal. If caught early, it can be removed with a wire brush without much effort. If excess corrosion is found covering the terminal and hardware, shut down the system by removing all charging and discharging connections from the battery, disassemble the battery hardware and cables, and thoroughly clean the terminal, hardware, and cable lug. A baking soda and water mixture can be applied to the corroded areas, which can then be scrubbed with a wire brush. However, be extremely careful that none of the baking soda mixture gets into the battery cells, as it will neutralize some of the electrolyte, reducing the battery’s performance. Finally, rinse all of the baking soda off with clean water and dry with a clean rag.

Comments (10)

I have a battery bank where one of the batteries appears to have a bad cell. The SG is low and the voltage across the battery is only 4.2v, these are 6v Trojan L16s. The rest of the batteries are in good shape - SG is good and voltage levels are consistent. I am going to replace the bad battery with a new one, fully charged. My question is, after I do that is there anything I should do for the entire battery bank?

Have you tried a full, 8-hr. equalization on the battery bank as it is? The cell may be weak, but without occasional equalization it will steadily get worse and worse.

If you end up replacing the battery, use the bank a few cycles as a break-in then go ahead and perform a full equalization on the bank. That will bring the older batteries up as close as possible to the level of the new battery. But if your battery has multiple strings, the bank will never be better than the lowest-performing string, even with a new battery within one of the strings.

I hear you Eric. But I am in a very harsh environment. Temps range from 0 in the Winter to 109 (sometimes) in the Summer. One day can have ranges of 70 degrees. My battery banks just don't preform as expected, even with diligent maintenance.
Please let me know your expert opinion on the Lithium as an alternative. I have been watching this technology but want to wait till it is perfected. Are there any other options.

Marsha,
I've supplied thousands of systems thoughout the world; many in extreme temperature environments. Your problem is not unique.
In high temperatures batteries will suffer extreme loss of useful life and in cold temperatures their capacity is diminished.
If the air temperature canot be controlled the best method of solving the high & low temperature extremes is to BURY the batteries in a container. Getting the batteries a couple of feet undergroung will minimize the temperature effects. You can reduce the battery's temperature by 25 F. in hot summer months and increase it by 25 F. in cold winter months.
In addition, use a battery temperature compensated charge regulator to optimize the charging voltage.
By doing this your battery will last at least 50% longer and help provide it's maximum capacity.
If you need further assistance please let me know.
Ed Mahoney

Hi Just a point to Jim and Elaine stack? Lithium batteries have no history yet? we do not even know how to dispose of them yet, they can be highly toxic and a fire hazard, but i understand what you mean about, lead acid batteries, which are incidentally 95% recycled now. thanks eric roberts

Use lithium batteries and you never need to water, they last much longer and are non hazardous. It's the 21st century and we have taken lead out of paint and even gasoline so don't use it.
Just mining it kills us. People say it gets recycles but that is a poor excuse since it gets in the air and everyplace. LEAD is one of the worst containments ever used.
Solar City used Tesla Lithium batteries for backup. Tesla is building a new battery factory that will make them 30% better or more in a few years. Invest in the future not the past.

I was recently moving my inverter and inadvertantly the pos and neg battery leads touched momentarily causing some sparking while they were on the ground. I know this is not good for the battery bank (I have 12 surrettee S-530s) but is there any specific way I can test the batteries to see if they sufferred any permanent damage?

Thanks for the reply Micheal. The sparking was just for a second or so but did melt a bit of the copper connector on the end of the cable. Batteries seem to be performing as usual but would you recommend any maintenance or testing I should be doing after this incident?